Emergency back-up power system for traction elevators

Abstract

An emergency power supply for a traction elevator system utilizes a microprocessor-based control arrangement with pulse-width modulator technology to create an efficient, cost-effective back-up power system for a traction elevator. The microprocessor-based control arrangement is used to sense a phase irregularity in the power supply. Upon sensing the phase irregularity, the microprocessor-based control arrangement disconnects the elevator system from the main power source and then generates a control signal to initiate the supply of back-up power. Once the elevator electrical system has been stabilized, the elevator control system will sense that recovery has occurred and will then provide an appropriate speed and direction command to the traction motor drive system.

What is claimed is: 
     
       1. A back-up power system for supplying an emergency power source to a traction elevator comprising:
 a source of DC input power; 
 a microprocessor-based control arrangement configured to recognize phase irregularities in an input power supply and subsequently generate a control signal to remove the input power supply from the traction elevator, the microprocessor-based control arrangement further operable to generate a power control signal; and 
 a back-up power generating means coupled to the source of DC input power and responsive to the power control signal for converting the DC input power signal into the emergency power source for the traction elevator, wherein the back-up power generating means sequentially switches the DC input power through a transistor arrangement to produce a set of separate sine waves separated in phase, with the power control signal used to control the energy transfer from the DC power source to the output sine waves. 
 
     
     
       2. The back-up power system as defined in  claim 1  wherein the emergency power is three-phase emergency power, using a set of three separate sine waves, separated by in phase by 120°. 
     
     
       3. The back-up power system as defined in  claim 2  wherein the back-up power generating means provides a control signal to the source of DC input power to create and maintain a correct phasing of the output sine waves.